Divert-air valves for recirculation of condensed fresh gas, optionally with recirculated exhaust gas, from the pressure side of a compressor of a turbocharger back to the suction side of the compressor, are widely known. The connection between the pressure side and the suction side of the compressor via a bypass line is required for the transition from a high load into the coasting operation of the internal combustion engine so as to prevent a high conveyance of the booster pump against a closed throttle flap and the resultant pumping effect, and to prevent a sudden drop of the turbo speed which is too strong with resulting thermodynamic problems.
Divert-air valves are frequently operated electromagnetically, wherein the valve closure body of the valve is moved via the armature by the electromagnetic force and can be lowered onto a valve seat and be lifted off therefrom, the valve seat being arranged in a flow housing between an inlet and an outlet of the compressor. Very fast switching is required in these divert-air valves because of the rapidly changing load conditions of the compressor. Divert-air valves are therefore preferably designed for equalized pressure. This is accomplished by providing openings in the control body via which the pressure applied to the control body from below will be conducted into the interior of the valve, wherein the effective diameters on both axial sides of the control body are also selected to be equal. The control body will consequently only be acted on by the force of a spring that is effective in the closing direction and by the force of the electric magnet that is effective in the opening direction. Very short opening and closing times will thereby be achieved if the design has been correctly designed. To establish such a pressure compensation, it is required that, at least in the closed state of the valve, the intervening space between the moving control body and the surrounding housing is sealed. This is realized by radial or axial sealing rings that are supported on a surface of the housing.
Such a valve is described, for example, in DE 10 2010 026 121 A1. The electromagnetic actuator of this divert-air valve is surrounded by a plastic housing which bears against a connection housing formed with an annular recess into which a further plastic housing portion, serving as a support ring, is inserted, the plastic housing portion surrounding the control body and accommodating a radial sealing ring with a V-shaped cross section. Care must be taken to maintain precise tolerances when producing the housing portion in order to be able to mount the support ring on the connection housing. The support ring comprises a form-locking connection to the connection housing in the region of the annular recess to prevent the housing components from falling apart during transport. Although this will facilitate the assembly process, it has the consequence that, via the gap between these components, gas may intrude from the housing interior into the laterally connected duct. Such a gas flow will also have the consequence that contaminated gas also intrudes into the gap. This might result in caking effects that will render it considerably difficult to remove a valve. Due to their low thermal resistance, the plastic parts used also tend to cause an increased sooting of the valve. Expensive plastic parts must alternatively be used.